Follicle stimulating hormone (FSH) is an α/β heterodimer produced only in pituitary gonadotropes, which comprise 3-8% of all pituitary cells. It is named for its ability to stimulate follicle growth and maturation in females. Follicle stimulating hormone stimulates the granulosa cells that surround and nurture the developing oocyte (egg) in the follicle. Spermatogenesis also relies heavily on FSH which induces sertoli cell division in early life. In later life, FSH works in conjunction with testosterone to stimulate sertoli cells to nurture spermatogonia as they develop into sperm. A number of hormones from the hypothalamus, gonads and the pituitary itself, help regulate FSH.
Current technology for increasing ovulation and birthing rates in mammals involves the timed injections of relatively expensive hormones that act like FSH, followed by an injection of human chorionic gonadotropin for ovulation. Increasing ovulation is useful when oocytes are collected from animals for the purpose of being injected with specific genes to produce valuable transgenic offspring or from elite breeding animals for subsequent in vitro fertilization and implantation into a foster parent. Increasing ovulation is also useful for animals such as pigs, where it is desirable to increase the litter size of breeding animals so that the corresponding numbers of breeding animals that must be maintained can be reduced. Increasing litter size is also useful for endangered species where the number of breeding animals in captivity is small. Accordingly, it would be extremely useful to provide a simple and effective approach for increasing the production of gametes in animals.